Preparation of V2O5 from converter slag containing vanadium
来源期刊:Rare Metals2018年第10期
论文作者:Chong Han Liang Li He Yang Xiang-Xin Xue
文章页码:904 - 912
摘 要:Preparation of V2O5 from converter slag (CS)was investigated through roasting, leaching, extracting, and precipitating processes. The corresponding roles of the parameters during every procedure were analyzed in detail.(NH4)2SO4 and KHSO4 were used as fusing agents to transform compounds containing vanadium into soluble species. Mass ratio of (NH4)2SO4 to CS, mass ratio of KHSO4 to CS, and roasting temperature during the roasting process can significantly influence leaching rate of vanadium (LRV). With H2SO4 as leaching agent, 99.2%vanadium in CS can be leached out under the optimum leaching conditions, which mainly refer to liquid-to-solid ratio, H2SO4 concentration, leaching temperature, and leaching time. Extracting and back-extracting processes were introduced to purify the vanadium from the H2SO4lixivium. Extracting rate of vanadium (ERV) greatly depends on iron powder concentration, pH, diisooctyl phosphate (P204) content, volume ratio of extractant to H2SO4 lixivium, and extracting time. By adding ammonium hydroxide, 94.0%vanadium in back-extracting solution can be separated in the form of precipitates. The product from the roasted precipitate mainly consists of V2O5, the content of which is higher than 90.0%.
稀有金属(英文版) 2018,37(10),904-912
Chong Han Liang Li He Yang Xiang-Xin Xue
School of Materials and Metallurgy,Northeastern University
作者简介:*Chong Han e-mail: hanch@smm.neu.edu.cn;
收稿日期:4 July 2014
基金:financially supported by the Fundamental Research Fund for the Central Universities (No. N130302004);the National Major International Cooperation Program of China (No. 2012DFR60210);the National High-Tech Research and Development Program of China (No. 2012AA062304);the National Natural Science Foundation of China (Nos. 51090384 and U1360204);
Chong Han Liang Li He Yang Xiang-Xin Xue
School of Materials and Metallurgy,Northeastern University
Abstract:
Preparation of V2O5 from converter slag (CS)was investigated through roasting, leaching, extracting, and precipitating processes. The corresponding roles of the parameters during every procedure were analyzed in detail.(NH4)2SO4 and KHSO4 were used as fusing agents to transform compounds containing vanadium into soluble species. Mass ratio of (NH4)2SO4 to CS, mass ratio of KHSO4 to CS, and roasting temperature during the roasting process can significantly influence leaching rate of vanadium (LRV). With H2SO4 as leaching agent, 99.2%vanadium in CS can be leached out under the optimum leaching conditions, which mainly refer to liquid-to-solid ratio, H2SO4 concentration, leaching temperature, and leaching time. Extracting and back-extracting processes were introduced to purify the vanadium from the H2SO4lixivium. Extracting rate of vanadium (ERV) greatly depends on iron powder concentration, pH, diisooctyl phosphate (P204) content, volume ratio of extractant to H2SO4 lixivium, and extracting time. By adding ammonium hydroxide, 94.0%vanadium in back-extracting solution can be separated in the form of precipitates. The product from the roasted precipitate mainly consists of V2O5, the content of which is higher than 90.0%.
Keyword:
Converter slag; V2O5; Roasting; Leaching; Extracting;
Received: 4 July 2014
1 Introduction
Vanadium can enhance physical properties of materials including tensile strength,hardness,and fatigue resistance,which promotes its extensive usage in ferrous and nonferrous alloys
In the last decades,many studies have been conducted to recover vanadium from steel slag
Recently,a new method called sub-molten salt (SMS)has been developed to recover vanadium from steel slag
To our knowledge,few papers investigated the whole procedure for preparing V2O5 from steel slag.In this work,V2O5 can be obtained from converter slag (CS) by means of several processes including roasting,leaching,extracting,and precipitating.CS containing vanadium was roasted after the addition of (NH4)2SO4 and KHSO4 which were rarely used as fusing agents in previous studies.Effects of both roasting and leaching conditions on the leaching rate of vanadium (LRV) were investigated in detail with deionized water or dilute sulfuric acid as the leaching agent.Changes in the extracting rate of vanadium (ERV)were also measured as functions of the extracting parameters.
2 Experimental
2.1 Materials and methods
CS was collected from Chengde Iron and Steel Plant,Hebei Province,China.After being crushed and ground,CS was sieved and its size was in the range of 0.096-0.120 mm.As shown in Table 1,chemical compositions of CS were analyzed using X-ray fluorescence (XRF,ZSX100e,Japan).Various chemical reagents,including (NH4)2SO4,KHSO4,H2SO4,ammonium hydroxide,NaOH,diisooctyl phosphate (P2O4),and tributyl phosphate (TBP;AR,Sinopharm Chemical Reagent Co.,Ltd.),were used during the processes of roasting,leaching,extracting,and precipitating.Sulfonated kerosene (SK) originated from the reaction of kerosene and concentrated sulfuric acid.
Table 1 Chemical compositions of CS (wt%)
2.2 Procedure
2.2.1 Roasting of CS
To transform compounds containing vanadium into soluble species,mixtures of CS,(NH4)2SO4,and KHSO4 were roasted in the furnace.(NH4)2SO4 and KHSO4 were used as the fusing agents to facilitate the transformation of compounds containing vanadium.Though the structure of KHSO4 was similar to that of (NH4)2SO4,the melting point(219℃) of KHSO4 was far less than that (513℃) of(NH4)2SO4.According to the theory of the eutectic mixture,KHSO4 can reduce the melting point of mixtures and enhance the reaction between (NH4)2SO4 and compounds containing vanadium.NH3 and SO2 originating from the decomposition of (NH4)2SO4 and KHSO4 can form NH3·H2O and H2SO4 through the reaction with water.H2SO4 and NH3-H2O can be reused as the leaching agent and precipitator in the following processes,respectively.To investigate the effects of the roasting conditions on changes in the solubility of compounds containing vanadium,mass ratio of (NH4)2SO4 to CS,mass ratio of KHSO4to CS,roasting temperature,and holding time varied in the range of 2-12,0-1.65,290-390℃,and 0-45 min,respectively.Mineral compositions of the fresh and roasted CS were analyzed through X-ray diffractometer (XRD,X'Pert Pro,the Netherlands).
2.2.2 Leaching of vanadium
The roasted mixtures were magnetically stirred and leached by the deionized water or sulfuric acid (1.5 mol·L-1) in the beaker.It was reported that the vanadium in steel slag can be leached as V02+and
Mineral compositions of the residue were also analyzed by X-ray diffractometer (XRD,X'Pert Pro,the Netherlands).Effects of liquid-to-solid ratio,H2SO4 concentration,leaching temperature,and leaching time on LRV were investigated in detail.
2.2.3 Extracting of vanadium
Several ions including Fe3+,Fe2+,and Ti4+may also be leached out during the leaching process.Thus,the vanadium should be further extracted from the H2SO4 lixivium through the appropriate method.The P2O4 existed in the form of the biopolymer ([H(C8H17)2PO4]2) in the kerosene.The H+in[H(C8H17)2PO4]2 can react with VO2+to form VO[(C8Hi7)2PO4]2 through the ion exchange
2.2.4 Preparation of V2O5
The pH of back-extracting solution was adjusted to 8.25through adding ammonium hydroxide.The precipitate would be continually formed when back-extracting solution was stirred for 45 min at 85℃.After being filtered using the filter paper,the precipitate was washed by the deionized water and dried in the oven.Then,the precipitate was roasted to prepare V2O5 for 2 h at 550℃in the furnace.It should be pointed out that the experimental data in four processes had slight errors within 3%.
3 Results and discussion
3.1 Effects of roasting conditions on leaching of vanadium
Figure 1 shows XRD patterns of the fresh and roasted CS.As shown in Fig.la,the main minerals containing vanadium in the fresh CS are MnV2O4,MgV2O4,Fe2VO4,FeV2O4,and V3O4.The fresh CS also contains iron-bearing compounds such as Fe3O4,Fe2SiO4,and Fe2TiO4.After the roasting process,vanadium mainly exists in the minerals of MgV2O5,CaV2O5,Ca3(VO4)2,and Mg(VO3)2(Fig.1b).Iron-bearing compounds are transformed into FeSiO3 and Fe2(SO4)3.Additionally,species containing calcium such as CaSiO3 and CaSO4 also appear.These results demonstrate that roasting process results in significant changes in mineral compositions in CS.
Fig.1 XRD patterns of a fresh CS and b roasted CS.Roasting conditions:roasting temperature of 350℃,holding time of 360 min,and mass ratio of CS,(NH4)2SO4,and KHSO4 of 1.00:8.00:0.67
Deionized water was used as leaching agent to investigate the effects of roasting conditions on leaching behaviors of vanadium in CS.Figure 2a shows the influences of mass ratio of (NH4)2SO4 to CS on LRV at mass ratio of KHSO4 to CS of 0.67,roasting temperature of 350℃,and holding time of 36 min.LRV increases from 34.5%to67.9%with an increase in mass ratio of (NH4)2SO4 to CS from 2 to 8,whereas it decreases from 67.9%to 57.1%with an increase in mass ratio of (NH4)2SO4 to CS from 8to 12.Figure 2b shows the effects of mass ratio of KHSO4to CS on LRV at mass ratio of (NH4)2SO4 to CS of 8,roasting temperature of 350℃,and holding time of36 min.LRV at mass ratio of KHSO4 to CS of 0.67 is larger by 11.5%than that without KHSO4.However,LRV decreases by 5.0%when mass ratio of KHSO4 to CS increases from 0.67 to 1.67.These confirm that there are the optimal dosages of (NH4)2SO4 and KHSO4 for the leaching of vanadium.The role of roasting temperature in LRV is summarized in Fig.2c when the mass ratio of CS,(NH4)2SO4,and KHSO4 is 1.00:8.00:0.67 and holding time is 36 min.LRV is 62.5%at 290℃,while it is 69.0%and is larger by 6.5%at 350℃.LRV decreases by 9.7%at390℃compared to that at 350℃.Li and Xie
Fig.2 Effects of roasting conditions on LRV:a mass ratio of (NH4)2SO4 to CS,b mass ratio of KHSO4 to CS,c roasting temperature,and d holding time
3.2 Leaching of vanadium from roasted CS using H2SO4
To enhance LRV of vanadium in the roasted CS,the deionized water was replaced by H2SO4 as the leaching agent.Figure 3a shows the effects of liquid-to-solid ratio on LRV at H2SO4 concentration of 6 vol%,leaching temperature of 90℃,and leaching time of 6 h.LRV increases from 87.3%to 91.6%with liquid-to-solid ratio increasing from 2 to 8 ml·g-.Nevertheless,LRV almost remains unchanged when liquid-to-solid ratio increases from 8 to 10 ml·g-1.Figure 3b summarizes the changes in LRV as a function of H2SO4 concentration at liquid-tosolid ratio of 8 ml·g-1,leaching temperature of 90℃,and leaching time of 6 h.LRV is 71.2%at H2SO4 concentration of 2 vol%,while it is 94.9%at H2SO4 concentration of 16 vol%.It can be noticed that LRV only increases by 1.1%with H2SO4 concentration increasing from12 vol%to 16 vol%.Under conditions with liquid-to-solid ratio of 8 ml·g-1,H2SO4 concentration of 12 vol%,and leaching time of 6 h,influences of leaching temperature on LRV are shown in Fig.3c.LRV at leaching temperature of95℃is larger by 34.5%than that at leaching temperature of 50℃.LRV at leaching temperature of 98℃exhibits a slight decrease when compared to that at leaching temperature of 95℃,which may be ascribed to an experimental error.Figure 3d shows the role of leaching time in LRV at liquid-to-solid ratio of 8 ml·g-1,H2SO4 concentration of 12 vol%,and leaching temperature of 95℃.LRV exhibits a significant increase with leaching time prolonging.However,LRV just increases by 0.5%when leaching time increases from 5 to 7 h.The above results definitely demonstrate that liquid-to-solid ratio,H2SO4concentration,leaching temperature,and leaching time have significant effects on LRV during the leaching process.During the leaching process of vanadium from the roasted mixtures of CS and Na2CO3,Aarabi-Karasgani et al.
Fig.3 Effects of leaching conditions on LRV:a liquid-to-solid ratio,b H2SO4 concentration,c leaching temperature,and d leaching time
Figure 4 shows XRD patterns of the residues under different leaching conditions.The peak at 35.117°is ascribed to species containing vanadium such as MnV2O4,Fe2VO4,and MgV2O4.The peak intensity significantly decreases with the increase in liquid-to-solid ratio,H2SO4concentration,leaching temperature,and leaching time.This indicates the decrease in the content of species containing vanadium in the residues,leading to the increase in LRV as shown in Fig.3a-d.However,the peaks of species containing vanadium incompletely disappear,which suggests that some of species containing vanadium remain in the residue due to the blocking by gangue minerals.Additionally,it is noticed that the peak intensity of SiO2 at21.915°shows an increase with the corresponding parameters increasing,suggesting the enrichment of SiO2 in the residues.Additionally,the residues also consist of minerals containing Fe,Si,and Ti.According to the previous studies
Table 2 reports LRV from the slag under the corresponding optimum conditions using different methods in previous studies and this work.LRV is in the range of 93.7%-95.0%using SMS technology with NaOH-NaNO3 or KOH as leaching agents
Fig.4 XRD patterns of leaching residues under different conditions:a liquid-to-solid ratio,b H2SO4 concentration,c leaching temperature,and d leaching time
Table 2 LRV from slag under optimum conditions using different methods
3.3 Extraction of vanadium from H2SO4 lixivium
As mentioned in experimental section,further purification of vanadium from H2SO4 lixivium is necessary due to the existence of other ions.Addition of iron powders in H2SO4lixivium is aimed to reduce
Fig.5 Effects of extracting conditions on ERV:a content of iron powders,b pH,c P204 content,d TBP content,e volume ratio of extractant to H2SO4 lixivium,and f extracting time
3.4 Preparation of V2O5
It was determined that vanadium can be separated from the solution in the form of ammonium metavanadate
Fig.6 XRD pattern of washed,dried,and roasted precipitates
Fig.7 Technology road map of preparation of V2O5 from CS
4 Conclusion
V2O5 can be obtained from CS through several processes including roasting,leaching,extracting,and precipitating.The LRV greatly depends on mass ratio of (NH4)2SO4 to CS (8),mass ratio of KHSO4 to CS (0.67),and roasting temperature (350℃),but not on holding time (36 min)during the roasting process.The numbers in parenthesis show the optimum values of the corresponding parameters.The parameters including liquid-to-solid ratio (8 ml·g-1),H2SO4 concentration (12 vol%),leaching temperature(95℃),and leaching time (5 h) can greatly affect LRV during the leaching process.LRV can reach 99.2%under the optimum leaching conditions.It is determined that iron powder concentration (2 g-L-1),pH (3.25),P204 content(15 vol%),volume ratio of extractant to H2SO4 lixivium(1),and extracting time (10 min) play important roles in the ERV during the extracting process.Through adding ammonium hydroxide,94.0%vanadium can be separated in the form of the precipitate from the solution.The product of V2O5 with the content of higher than 90.0%can be prepared by roasting the precipitate.
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